The Boeing Company (“Boeing”) has developed many high performance, low cost, compact phased array antenna modules. The antenna modules shown in FIGS. 1a–1c have been used in many military and commercial phased array antennas from S-band to Q-band. These modules are described in U.S. Pat. No. 5,886,671 to Riemer et. al. and U.S. Pat. No. 5,276,455 to Fitzsimmons et. al., both herein incorporated by reference.
The in-line first generation module has been used in a brick-style phased-array architecture at K-band and Q-band. The approach shown in FIG. 1a requires elastomeric connectors for DC power, logic and RF distribution but it provides ample room for electronics. As implemented in FIG. 1a, the in-line module provides only a single beam, either linear or right-hand or left-hand circularly polarized. As Boeing phased array antenna module technology has matured, many efforts have resulted in reduced parts count, reduced complexity and reduced cost of several key components. Boeing has also enhanced the performance of the phased array antenna with multiple beams, wider instantaneous bandwidths and improved polarization flexibility.
The second generation module, shown in FIG. 1b, represents a significant improvement over the in-line module of FIG. 1a in terms of performance, complexity and cost. It is sometimes referred to as the “can-and-spring” design. This design provides dual orthogonal polarizations in a more compact, lower-profile package than the in-line module. The can-and-spring module forms the basis for several dual simultaneous beam phased arrays used in tile-type antenna architectures from S-band to K-band. The fabrication cost of the can-and-spring module has been reduced through the use of chemical etching, metal forming and injection molding technology. The third generation module developed by Boeing, shown in FIG. 1c, provides a low-cost dual polarization receive module used in high-volume production at Ku-band.
Each of the phased-array antenna module architectures shown in FIGS. 1a–1c require multiple module components and interconnects. In each module, a large number of vertical interconnects such as electrically conductive fuzz buttons and springs are used to provide compliant DC and RF connectivity between the distribution printed wiring board (PWB), ceramic chip carrier and antenna probes.
A further development directed to reducing the parts count and assembly complexity for single antenna modules is described by Navarro and Pietila in U.S. application Ser. No. 09/915,836, presently allowed, and assigned to Boeing. The subject matter of this application is also incorporated by reference into the present application and involves an “Antenna-integrated ceramic chip carrier” for phased array antenna systems, as shown in FIG. 1d. The antenna integrated ceramic chip carrier (AICC) module combines the antenna probes of the phased array module with the ceramic chip carrier that contains the module electronics into a single integrated ceramic component. The AICC module eliminates vertical interconnects between the ceramic chip carrier and antenna probes and takes advantage of the fine line accuracy and repeatability of multi-layer, co-fired ceramic technology. This metallization accuracy, multi-layer registration can produce a more repeatable, stable design over process variations. The use of mature ceramic technology also provides enhanced flexibility, layout and signal routing through the availability of stacked, blind and buried visa between internal layers, with no fundamental limit to the layer count in the ceramic stack-up of the module. The resulting AICC module has fewer independent components for assembly, improved dimensional precision and increased reliability. The inline module, can-and-spring module, the molded module, and the AICC have been realized as single element modules. So far, the AICC has been implemented by Boeing as a single element phased array module which is connected to the printed wiring board and honeycomb in much the same way as the can-and-spring and injection-molded modules. The AICC approach provides manufacturing scalability from single to multiple elements. As manufacturing/assembly process yields increase, the AICC can be scaled from single to multiple element sub-arrays to reduce parts count and assembly complexity.
A Boeing antenna which departs from a single element module is described by Navarro, Pietila and Riemer in U.S. Pat. No. 6,424,313, also incorporated by reference herein, which is shown in FIG. 1e. This module is referred to within Boeing as the “3D flashcube”. It has been implemented as a four-element module to provide additional space for electronics. This approach also avoids the use of fuzz buttons and button holders for its vertical interconnects. It has been used successfully to provide two independent simultaneous receive beams at 21 GHz with +/−60° scanning. It has also been implemented at 31 GHz in a switchable transmit application with +/−60° scanning. The 3D flashcube model can also be used to implement more than two independent receive and/or transmit beams.
In FIG. 1f, Boeing-Phantom Works further combines many more functions of a phased array antenna into a single component through an approach known as the “Antenna Integrated Printed Wiring Board” (“AIPWB”). This approach is disclosed in U.S. application Ser. No. 10/007,067, presently pending, which is also incorporated by reference into the present application. The approach reduces parts count and further improves alignment and mechanical tolerances during manufacturing and assembly. The improved alignment and manufacturing tolerances improves yield and electrical performance while the reduced parts count shortens assembly time and reduces the number of processing steps required to manufacture the antenna module. This ultimately lowers the overall phased array antenna system costs. The AIPWB approach can be scaled to larger sub-arrays without degrading performance and represents an important step in the direction of more easily and affordably manufactured phased array antenna systems.
The first generation module in FIG. 1a is the standard single polarization in-line or brick architecture used extensively for many electronic phased array systems because of the ample room provided for electronics. FIGS. 1b, 1c and 1d uses a tile-type or planar architecture which naturally provides dual polarization. A drawback of the tile architecture is that space is severely limited as frequency and scanning angle increases since the electronics and input/output pads must fit within the physical area of the radiators in the array lattice. Because of the additional input and output pads required to connect to the RF/DC power/logic distribution, single element modules are further constrained in dimensions. As the array dimensions increase, the single element module pads require tighter dimensional tolerances to ensure alignment and connectivity.
FIG. 1e shows another deviation from the single element tile-type modules. It has some of the benefits of tile-type architectures by providing dual polarization and broad-side interconnections to the printed wiring board. It also has some of the benefits of the in-line architectures by providing ample area for electronics and transitions. The 3D flashcube concept has been realized as a quad-module but the approach can be increased to 2×N modules as yield in electronics and packaging increase. The 3D flashcube uses a three layer flexible stripline to provide connections from the electronics to the antennas as well as connections from the electronics to the printed wiring board.
However, even with the 3D flashcube implementation, it is difficult to provide the extremely tight antenna module spacing between adjacent antenna modules that is needed to achieve +/−60° scanning in the microwave frequency spectrum (e.g., 60 GHz). The limitation of using the three layer flexible stripline for interconnections is that as scan angles and frequencies increase, the stripline must be bent at very, very tight (i.e., small) bend radii in order to achieve the extremely close antenna module spacing required for +/−60° scan angle performance in the microwave frequency spectrum. The stripline ground plane and conductor line can break apart at the very small bend radii which is needed to accomplish the extremely tight radiating element spacing necessary for +/−60° scanning at microwave frequencies.
Accordingly, there still exists a need in the art for a dual polarized, phased array antenna which is able to operate within the V-band frequency spectrum (generally between 40 GHz–75 GHz), and more preferably at 60 GHz, while providing at least +/−60° grating-lobe free scanning. Such an antenna, however, requires a new packaging scheme for coupling the electronics of the antenna to the radiating elements in a manner that accommodates the very tight radiating element spacing required for 60 GHz operation, while still providing adequate room for the electronics associated with each antenna module.